Control for lens edging machine



Nov. 15, 1955 B. w. JONES 2,723,502

CONTROL FOR LENS EDGING MACHINE Filed Nov. 50, 1954 2 Sheets-Sheet 1 F 4 Powen SUPPLY INVENTOR. B U R R W. JON E5 ATTORNEY Nov. 15, 1955 B. w. JONES 2,723,502

CONTROL FOR LENS EDGING MACHINE Filed NOV. 50, 1954 2 Sheets-Sheet 2 FIC5.2

INVENTOR. BURR W. JONES BY M ATTORNEY United States Patent CONTROL FOR LENS EDGHJG MACHINE Burr W. Jones, Livonia, N. Y., assignor to Bausch & Lomh Optical Company, Rochester, N. Y., a corporation of New York Application November 30, 1954, Serial No. 472,029

6 Claims. (Cl. 51-101) This invention relates to lens edge grinding machines and more particularly it has reference to improvements in the apparatus for controlling the rotation of a lens on said machines.

Many edge grinding machines are provided with an apparatus for controlling the grinding of the edge of a rough cut lens blank to a prescribed configuration during a single revolution of said blank. Since the amount of material to be removed van'es around the lens periphery due primarily to different thicknesses at different positions on the lens blank, it is necessary to permit the thicker I areas of the blank to dwell longer in contact with the grinding wheel. This result is presently achieved by a control mechanism that is adapted to vary the rate of rotation of the lens blank to allow thicker areas of the lens periphery to dwell longer in grinding contact with the grinding wheel. These mechanisms are controlled by making or breaking the electrical circuit between the power supply and the driving motor when a former is engaged with or disengaged from an abutment block for increasing or decreasing the rate of rotation of the lens blank. However, when this electrical circuit between the former and block is made or broken, electrical arcing and chattering occurs therebetween which destroys the surface of the former and impairs the operation of the mechanism. Various devices have been proposed to avoid the aforementioned disadvantages but each new device involves equally serious defects.

It is, therefore, an object of this invention to overcome the aforementioned difficulties and to provide a lens edge grinding machine having an improved control mechanism whereby the excess material is removed from the edge of a rough cut lens blank during a single revolution of the blank.

It is another object of this invention to provide a lens edge grinding machine having an improved control B mechanism of the type described that is governed by the vibrations produced by the grinding of the lens.

It is a further object of this invention to provide a lens edge grinding machine having an improved control mechanism of the type described that is simple and economical to manufacture and maintain and is efiicient and reliable in operation.

These and other objects and advantages reside in certain novel features of construction, arrangement and combination of parts as will hereinafter be more fully described and pointed out in the appended claims.

Referring to the drawings:

Fig. 1 is a front elevation of an edge grinding machine embodying one form of my invention, with parts shown in section and the electrical circuit diagrammatically shown.

Fig. 2 is a sectional view of the grinding machine taken on the line 2-2 of Fig. 1.

Fig. 3 is a diagrammatic illustration of an ophthalmic lens blank with the outline of the finished lens superposed thereon.

Fig. 4 is a schematic view of a modified form of my ice invention with parts shown in section and the electrical circuit diagrammatically shown, and

Fig. 5 is a sectional view taken on the line 55 of Fig. 1.

A preferred form of my invention is shown in Figs. 1 and 2 of the drawings wherein my improved control mechanism is mounted on a lens grinding machine which rests on a base 11 having a grinding wheel 12 mounted on a shaft 13 which is rotatably supported in a pair of bearings 14. Upstanding from said base 11 is a pair of brackets 15, only one being shown, between which is swingably mounted a carriage 16, as best shown in Fig. 5, supported by a hollow sleeve 17 which passes through both a bore 18 in the bracket and. a bore 19 in the carriage 16. The carriage 16 has a pair of arms 20 and 21 terminating, respectively, in the bearing bosses 22 and 23 which support a chucking device comprising a pair of spaced, aligned shafts 24 and 25 coaxial with respect to each other. A lens blank 26 is removably held between the heads 27, 28 of the shafts 24 and 25 by means of a conventional lens chuck or clutch arrangement, not shown.

In Fig. 3 is shown a lens blank 29, as received from a lens supplier, on which is drawn, for illustration purposes, the final configuration of the lens 26. The rough line 26 represents the crumbled away edge of the original lens blank and results in a blank that is referred to in the art as a rough cut lens blank. The nature of a prescription in most lenses is such that certain edge areas of the rough cut blank are thicker than other areas, for instance, at A in Fig. 3, the blank may be 3 mm. thick while-at B the blank may be only 1 mm. thick. The rough cut blank is in substantially this aforementioned condition of thickness and edge configuration when it is mounted for edging on the edge grinding machine.

The shaft 24, which rotates lens blank 26, has a driven gear 30 in'mesh with a drive gear 31 fixed on a drive shaft 32 which is journaled at one end in a bore 33 in the sleeve 17 and at the other end in a bracket 34 upstanding from the base 11. The drive shaft 32 is rotatably driven by an electric motor 35 through a power shaft 36, a pair of helical gears 37, 38 and a clutch mechanism 39, so that the chucking device is operatively connected to said motor for rotating the lens. Said clutch 39 is of conventional construction and is used to manually engage or disengage the drive means between the motor 35 and the shaft 32.

On the outer end portion of shaft 24 of the chucking device is demountably fixed, preferably by a suitable clamp nut 49, a pattern or former having a prescribed configuration corresponding to the final desired profile of the lens 26. The carriage 16 is swingably mounted about the sleeve 17 so that the lens 26 will be moved into contact with the grinding wheel 12 by means of a tension spring 21 which is anchored in any preferred manner to the arm 21 at one end and to the base 11 at the other end, as shown in Fig. 5. This motion of the carriage is limited by the former 50 engaging with a stationary abutment block 51 on the machine whereby the profile of the former is transferred to the lens 26 as these members turn together through a complete revolution.

According to my invention, a novel control device is provided for deactivating the motor 35 when the lens blank emits vibrations upon touching the rotating grinding Wheel 12. The control device comprises a sensing member of the vibro-electric or microphonic type of vibration converter or transformer 52, preferably of the crystal controlled type such as the commercially known Contact Vibromike. It is also within the purview of this invention to utilize any acoustic or audio type sensing device, which does not necessitate a direct contact on the lens 26 or part of the lens carriage or chucking device, and is supported freelv or otherwise within sound-receiving distance of the noise or air vibrations caused by the grinding operation. Such acoustic sensing devices cornprise telephonic or microphonic receiving instruments and other sound-actuated electrical switches and relays. The above-mentioned preferred form of said sensing member is constructed and arranged to receive mechanical vibrations and convert them into electrical impulses. The sensing member 52 has a contact arm 53 which is held lightly against the chucking device or shaft head 27 in the immediate vicinity of the lens. Said member 52 is held in correct position on the carriage 16 by a mounting bracket 54 which is attached to the bearing boss 22 by screws 55. It is to be understood that the term sensing member includes both an audio responsive mechanism that utilizes the noise or air vibrations emitted by the grinding of a lens as well as a mechanism which utilizes mechanical vibrations produced by the grinding of a lens.

Extending from a power supply to the motor 35 is an electrical circuit which has a solenoid operated switch 56 therebetween for making and breaking the electrical connection between the motor 35 and power supply. The switch 56 has a pair of main contacts 59 and 60 connected to the motor 35 and power supply by conductors 61, 62 and 63. The main contacts 59 and 60 are normally bridged by a movable switch blade 64 which is held in closed position by a spring 65. A solenoid 66, when activated or energized by the electrical impulses from the vibration converter 52, produces enough pull to lift the switch blade 64 from contacts 59 and 60 against the force of Spring 65 to thereby break the electrical connection between the power supply and the motor 35 for stopping the operation of the motor and the rotation of the lens.

In order to provide ample power to actuate the solenoid 66, the electrical output of the converter 52 is preferably strengthened by an amplifier unit 67 of ordinary commercial design. The electrical impulses from the converter 52 are conducted by leads 57, 58 to amplifier 67 where said impulses are amplified and passed to the solenoid 66 through the leads 68 and 69. It is to be understood that when an amplifier is used, it should be matched in performance characteristics to the particular type of vibro-electric converter and solenoid switch chosen for the control device. The single stage, grid controlled amplifier shown in the drawings is merely exemplary of a device suitable for the amplifying function. A main cutoff switch 70 is provided between the power supply and amplifier 67.

In operation, the grinding wheel 12 is set in motion and the main switch 70 is closed to energize the motor 35 through the electrical circuit from the power supply. The carriage 16 is swung about its pivot sleeve 17 to bring the edge of the lens blank 26, being rotated by motor 35, into grinding contact with the grinding wheel 12. The grinding of the edge of the lens 26 will produce mechanical vibrations in the chucking shaft 24 which are picked up and transmitted by the contact arm 53 to the sensing member or converter 52 where said vibrations are changed into electrical impulses. The resulting electrical impulses are conducted by the leads 57 and 58 to the amplifier 67 where they are amplified. Leads 68 and 69 carry the amplified impulses from the amplifier 67 to the solenoid 66 for energizing said solenoid whereby the switch 56 in said electrical circuit is opened to thereby stop the operation of the motor and the rotation of the lens. With the lens 26 not rotating, the gringing wheel 12 continues to grind the same area on the periphery of the lens blank until snfficient stock is removed to allow the former 50 to engage the stationary abutment block 51. Upon contact between the former and block, the lens blank 26 is held slightly away from the grinding wheel 12 so that grinding of the lens blank stops. When the intensity of the grinding noise and vibration is reduced to an insensible amount, the sensing member or converter 52 ceases to operate so that the solenoid 66 is deenergized. Upon deenergization of the solenoid 66, the spring 65 closes the switch 56 to permit electrical energy from the source to operate the motor 35 which rotates the lens 26 until an adjacent higher peripheral area of the lens is brought into contact with the grinding wheel whereupon grinding is resumed. The resulting vibrations again deactive the motor 35 as above described to hold the lens in the new grinding position. One complete revolution of the blank, repeating this sequence of operations several times, will produce a finished lens 26.

Fig. 4 shows a second embodiment of my invention comprising a vibrating reed type of sensing member or vibroelectric converter 72 controlling a solenoid switch 73 for activating the driving member or motor 35 for rotating the lens blank 26.

An electric circuit connects the power supply and the motor 35 through the main switch 70, sensing member or converter 72 and the solenoid operated switch 73. From the power supply and main switch 70, one lead 74 runs to one side of the motor 35 and to the contact 75 of the converter 72, the other lead 76 runs to one side of a solenoid 77 and through a pair of contacts 78, 79, and lead 79 to the other side of the motor. A separate lead 80 runs from the contact 81 of the converter 72 to the solenoid 77.

The sensing member or vibro-electric converter 72 comprises a housing 82 which is mounted by means of the bracket 83 and screw 84 on the bearing boss 22 of the carriage 16 in operative position relative to the chucking device or shaft 24. An adjusting bolt 85 extends through the bracket 83 and into a base portion 86 in one end of the housing whereby the converter 72 is adjustably positioned relative to and in engaging relation with the head 27 of the shaft 24 in the immediate vicinity of the lens. A flexible metal blade 87, fastened in the base portion 86 in the housing, has a weight 88 on one end portion and the electrical contact point 75 on a medial portion thereof. Also mounted in the housing 82, lying parallel to and spaced from the blade 87, is the fixed bar 89 which has one end portion fastened in base 86 and the other end portion supporting the electrical contact 81 in alignment with contact 75 on blade 87. Spacers 90, supporting the spring blade 87 in spaced relation from the housing and from the bar 89, are held in position by the rivet 91 extending through the base portion of the housing 82. Said housing 82 is tightly sealed and charged with an inert gas, such as argon, whereby the contacts 75 and 81 will not be damaged by arcing at the moment of separation.

It will be noted that the distance from the weight 88 to to base 86 is considerably longer than the distance from said weight to contact 81. With the weight 88 and blade 87 pivoting about the base 86 as a center, the weight 88 will oscillate with a normal frequency until on the upswing the contact 75 engages with contact 81 whereupon the momentum of the weight and the shorter length of the blade 87 will snap the weight up and down rapidly, so that the length of time the contacts 75 and 81 are engaged will be much shorter than the length of time they are not engaged. When the lens 26 is being ground, the weight 88 will be oscillated by the mechancial vibrations created by said grinding so that the contacts 75 and 81 will be engaged only for short intervals so that brief pulsations of current will flow to the solenoid 66. When the lens is not being ground, the contacts 75 and 81 will be in continual engagement to complete the circuit from the power supply through the converter 72 to the solenoid operated switch 73.

The solenoid operated switch 73 comprises a frame 92 having the solenoid 77 and a core 93 acting on a spring loaded armature 94 which depresses contact 79 connected to the motor 35 through the lead 79'. The upper end of the B? 3 is provided with a copper ring or slug 93' which produces a short time delay in the action of the arm ure 94 1 11 as at ommon y o n in slqwaeti lg relaysj Said contact 79 is adapted to be engaged with the contact 73 on the frame w'hich is connected by lead 76 to the power supply, so, that, when current flows through the closed contacts 75 and 8,1 of the converter 72, the solenoid 77 is energized which pivots the armature 94 to move contacts 78, 79 into closed position, this completing the circuit to the motor for driving the motor and rotating the lens.

This form of my invention is operated by moving the lens 26 into contact with the grinding wheel 12 by swinging the carriage 16 about pivot sleeves 17 under the influence of spring 21 as shown in Fig. 5. As the lens is ground by the grinding wheel, mechanical vibrations will be emitted that will vibrate the sensing member or converter 72 and start the weight and blade oscillating. Oscillation of the weight will not permit sufiicient current to flow through the contacts 75, 81, so the motor 35 will not operate and the lens will be ground at the same peripheral area. When that particular area of the lens is sufliciently ground to permit the former 50 to hold the lens out of contact with the grinding wheel, the vibrations will cease and the contacts 75, 81 will close to permit current to flow from the power supply through the converter to energize the solenoid. After a short delay caused by the influence of the copper ring 93, the solenoid will pivot the armature 94 to close the contacts 78, 79 for completing the circuit to the motor and thereby permit the motor to rotate the lens until the lens is again being ground. The resulting vibrations will break the contact between 75 and 81 and stop the operation of the motor and the rotation of the lens.

From the preceding description, it is apparent that I have provided an improved lens edging machine having advantageous means for utilizing the vibrations which are created by the grinding of the lens so that said vibrations control the rotation of the lens blank during the grinding operation. The control mechanisms are simple and compact, are economical to manufacture and maintain and are efiicient and reliable in operation, all of which is in fulfillment of the objects of this invention.

Although but certain forms of my invention have been shown and described in detail, it is apparent that other forms are possible and changes may be made in the details and arrangement thereof and substitutions may be made therein without departing from the spirit of the invention as claimed herebelow.

I claim:

1. In a lens edging machine the combination with a base, a grinding wheel rotatably mounted on said base, holding means carried by the base for rotatably supporting a lens in position to be edged by said grinding wheel and driving means for rotating the lens of means for controlling the operation of said driving means comprising sensing means responsive to the vibrations created by the grinding action of the Wheel on the edge of the lens, said sensing means being constructed and arranged to receive said vibrations and being operatively connected to said driving means whereby grinding of the lens will produce vibrations in said sensing means for controlling the operation of the driving means.

2. In a lens edging machine having a rotatable grinding wheel, a carriage for rotatably holding the edge ofa lens in contact with the wheel and a motor for rotating the lens, the combination of means for controlling the opera tion of the motor comprising a vibration sensing means carried by said machine adjacent to the wheel and the lens for receiving vibrations caused by the grinding action of the wheel on the lens, means for converting said vibrations into electrical impulses, and means for utilizing said impulses to stop the motor and thereby hold the lens stationary so that the grinding action will take place on a localized part of the edge of the lens.

3. In a lens edging machine having a base, a grinding wheel rotatably mounted on said base, a carriage movably mounted on said base, chucking means on said carriage for rotatably supporting a lens to be edged by said grinding Wheel, means urging said carriage towards said grinding wheel for engaging the edge of the lens with the grinding wheel, and driving means operatively connected with said chucking means for rotating the lens, the combination of means for controlling the operation of said driving means comprising sensing means responsive to the vibrations created by the grinding of the lens, said sensing means being mounted in close proximity to said wheel and said lens, said sensing means being operatively connected to said driving means whereby grinding of the edge of the lens will produce vibrations in said sensing means to control the operation of the driving means.

4. In a lens edging machine having a frame, a rotatable grinding wheel on the frame, a carriage mounted on the frame to move towards and away from the wheel, chucking means on the carriage for rotatably holding a lens, means for moving the carriage to bring the edge of the lens into contact with the wheel, a former carried by the carriage for simultaneous rotation with the lens and adapted to engage an abutment block on the frame for limiting the movement of the carriage towards the wheel, and a motor for rotating the lens and former, the combination of means for controlling the operation of the motor comprising vibration sensing means carried by the carriage adjacent the lens for receiving vibrations caused by the grinding action of the wheel on the lens, and means responsive to such vibrations for deenergizing the motor so that grinding action is confined to a localized part of the edge of the lens and continues until the engagement of the former with the abutment prevents further grinding so that the motor is again energized and the lens rotated to bring another portion of the lens edge into contact with the grinding wheel.

5. In a lens edging machine the combination of a base, a grinding Wheel rotatably mounted on said base, a carriage movably mounted on said base, chucking means on said carriage for rotatably supporting a lens to be edged by said grinding wheel, means urging said carriage towards the griding wheel for engaging the lens with the grinding wheel, a motor operatively connected with said chucking means for rotating said lens, means for controlling the operation of the motor comprising a switch in an electric circuit between said motor and a power supply, a solenoid member acting on said switch to open and close said switch for making and breaking the circuit to said motor, and a vibration actuated means mounted on the carriage and having a portion thereof in contact with the chucking means in the immediate vicinity of the lens, said vibration actuated means being operatively connected to the solenoid whereby grinding of the lens will produce vibrations in said vibration actuated means for energizing the solenoid for controlling the operation of the motor.

6. In a lens edging machine the combination of a base, a grinding wheel rotatably mounted on said base, a carriage movably mounted on said base, chucking means on said carriage for rotatably supporting a lens to be edged by said grinding wheel, a former mounted on said chucking means for simultaneous rotation with the lens and having an outside configuration corresponding to the desired configuration of the lens, an abutment block mounted on the base for selectively engaging with said former for limiting the movement of the lens toward the grinding wheel, means urging said carriage towards said grinding wheel for engaging the lens with said grinding wheel, a motor operatively connected with said chucking means for rotating the lens and former, means for controlling the operation of the motor comprising a switch mounted in an electric circuit between said motor and a power supply, means normally urging the switch into closed position to permit the motor to rotate the lens, a solenoid, means for energizing said solenoid to open said switch for breaking the electrical circuit to the motor, said last-named means comprising a vibration activated converter mounted on the carriage in engaging relation with the chucking means in the immediate vicinity of the lens, said converter being adapted to receive vibrations from the grinding of the lens which will be converted into electrical impulses for energizing said solenoid for opening the switch and stopping the operation of the motor as long as the vibrations continue so that when the former contacts the abutment block References Cited in the file of this patent UNITED STATES PATENTS Plimmer Dec. 20, 1932 Ellis Sept. 29, 1953 

